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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>


    <script>
        var a=['a','b']; 'a,b'  
        var b=['a','b'];

        // console.log('ab'==='ab');
        // console.log(a.join(',')===b.join());

       console.log(a);
       
       var c= a.join().split(','); 

       console.log(c);

       var d='a,b'; 
       console.log(d.split(','));

       console.log(a.join('')); //'ab'
    </script>
</body>

</html>